Direct conversion modulation schemes are popular since they can reduce filtering requirements and lend themselves to miniaturization. However, such schemes may not be as attractive for use with spectrally efficient modulation systems (e.g., single sideband (SSB)) that value better control of out-of-band spectral emissions. For example, fixed frequency direct conversion systems for generating SSB signals typically make use of a radio frequency (RF) filter to attenuate unwanted sidebands. These systems may be suitable for narrow band analog voice applications where the passband may be 3 KHz and the lower cutoff frequency is about 300 Hz, but impractical for wideband digital signals where the passband may be 6 MHz and frequency components can exist down to about zero Hertz. The RF filtering required to attenuate the unwanted sideband products may not be readily achievable for this application even at a fixed frequency and may be even more impractical for variable frequency applications.